Bletchley Park

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During World War II, British cryptographers at Bletchley Park broke a large number of Axis codes and ciphers, including the German Enigma machine. For this purpose, the mansion at Bletchley Park, pictured here, was soon joined by a host of other buildings. The mansion's fašade is an idiosyncratic mix of architectural styles.

Bletchley Park (BP) was the site of a secret British military intelligence operation during and just before World War II (WWII). The site was named after the mansion in the grounds of which it was established. While the mansion was part of the operation, many other buildings had to be erected to accommodate those employed on the site, these buildings were so temporary in nature that they were referred to as huts. The site is now a museum. It is located in the town of Bletchley, now in Milton Keynes, England.

During World War II, Bletchley Park was the site of the United Kingdom's efforts to break cyphers, particularly the Enigma and Lorenz cyphers used by Nazi Germany. The estate was conveniently located on a railway line (now closed) between the Universities of Oxford and Cambridge, which supplied many of the code breakers. It was also chosen for its proximity to a major road (the A5) to London and to a route for telephone trunk lines.

Bletchley Park has been credited variously with shortening the war by two years (possible due its contributions during the Battle of the Atlantic, but distinctly controversial), with ending the bombing of Pearl Harbor by sending information of the location of Yamamoto, the head of the Japanese Combined Fleet (although some information which led to his death came from breaks into JN-25 largely by USN cryptanalysts and happened long after December 7, 1941). Bernard Montgomery would often talk of how the code-breaking efforts of Bletchley Park enabled him to 'know what the Jerries [Germans] are having for breakfast'.


Before Station X

The Bletchley Park estate had been a manor since the Norman invasion. The earliest known reference is in 1308 [1] (, when it was owned by the de Grey family. It is also known that Browne Willis was lord of the manor in the early 18th century, some of his buildings (now lost) dating from 1711. The manor was at some time appropriated by the Crown. The present mansion was built between 1883 and 1926 by Herbert Samuel Leon (1850-1926), a financier and Liberal MP, who extended the red brick farmhouse of 1860 [2] ( Its style is a mixture of Victorian Gothic, Tudor and Dutch Baroque and was the subject of much bemused comment from those who worked there, or visited, during WWII. Leon's estate covered 581 acres (2.4 km²), of which Bletchley Park occupied about 55 acres (0.2 km²). Leon's wife died in 1937 [3] (, and in 1938 the site was sold to a builder, who was about to demolish the mansion and build a housing estate. However, just in time, Admiral Sir Hugh Sinclair, the Director of Naval Intelligence, head of MI6 and founder of the Government Code and Cypher School, knowing that war was imminent, bought the site with his own money in the Spring of 1938. The fact that Sinclair, and not the Government, owned the site was not revealed until 1997 when a trust was set up to save the site from redevelopment.

Wartime history

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The cottages in the stableyard were converted from a tack and feed house. Early work on Enigma was performed here by Dilly Knox, John Jeffreys and Alan Turing.

The Government Code and Cypher School (GC & CS), the intelligence bureau responsible for interception and decryption of foreign transmissions amongst other things, moved into the main house in 1939. Until he broke down, the Sinclair's private chef made early service at BP something to remember fondly. The radio station that was constructed in the park for its use was given the code name "Station X", a term sometimes erroneously applied to the code-breaking efforts at Bletchley as a whole. (It was called Station X because it was the tenth in a series of radio stations, X being the Roman numeral for ten.) Station X itself was soon moved south to Whaddon Hall, to divert attention from the Bletchley Park site. Additional listening stations such as the ones at Chicksands and Beaumanor Hall, the War Office "Y" Group HQ, also gathered raw signals for processing at Bletchley. To further the disguise of Bletchley Park, it was built to appear as a hospital from above to deter bombing by German planes. However, a bomb was dropped next to the despatch riders' entrance, shifting the whole of Hut 4 (the Naval Intelligence hut) two metres on its base. The bomb was thought to have been intended for Bletchley railway station.

The first Government visitors to Bletchley Park described themselves as members of Captain Ridley's shooting party. The intelligence produced from decrypts at Bletchley was eventually code-named "ULTRA".

Hugh Sebag-Montifiore, author of the book Enigma, is Leon's grandson. His book contains several photographs of the manor, before, during, and after WWII.


Among the famous mathematicians and cryptanalysts working there, perhaps the most influential and certainly the best-known in later years was Alan Turing. In 1943, the Colossus, the world's first programmable digital electronic computer, was designed at Bletchley Park by Max Newman and his team. The computer was designed and built to help break the Fish Cyphers, in particular the Lorenz cipher. Tommy Flowers of the British Post Office, whose crew actually built the computer(s) at its Dollis Hill facility, is said to have been the biggest influence on the building of an electronic computer, as he introduced the electronic valve - a device considered too unreliable until its use in the Colossus.

It is thought that at the height of the codebreaking efforts during the war, more than 10,000 people worked at Bletchley Park. They were selected for various intellectual achievements, whether they were chess champions, crossword experts, polyglots or great mathematicians. Some of them are said to have completed a five-year course in Japanese in just six months.

The Bletchley Park effort was comparable in influence to other WWII-era technological efforts, such as the crytographic work at Arlington Hall, the Naval Communications Annex (both in Washington, DC, and both in commandeered private girls' schools), the development of sophisticated microwave radar at MIT's Radiation Lab, and the Manhattan Project's development of nuclear weapons.

At the end of the war, much of the equipment used and its blueprints were destroyed by order, it is said, of Churchill. Though thousands of people were involved in the decoding efforts, the participants remained silent for decades about what they had done during the war, and it was only in the 1970s that the work at Bletchley Park was revealed to the general public. After the war, the site belonged to several owners, including British Telecom and the Civil Aviation Authority [4] (

The Bletchley Park Trust has been founded to further the maintenance of the site as a museum devoted to the code breakers. The Trust is volunteer-based and relies on public support to continue its efforts.


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Hut 6 in 2004.

The huts were designated by numbers; these quickly became associated as much with the work which went on inside the buildings as with the buildings themselves. Because of this, when a section moved from a hut into a larger building, they were still referred to by their "Hut" code name.

Some of the hut numbers, and the associated work, are:

  • Hut 1 — the first hut, built in 1939; translation
  • Hut 2 — recreational hut
  • Hut 3 — intelligence: translation and analysis of Army and Airforce Enigma decrypts
  • Hut 4 — Naval intelligence: analysis of Naval Enigma decrypts
  • Hut 5 — Army intelligence
  • Hut 6 — Cryptanalysis of Army and Airforce Enigma
  • Hut 7 — Punched card machines
  • Hut 8 — Cryptanalysis Naval Enigma
  • Hut 9 — Pay and administration
  • Hut 10 — Meteorological section
  • Hut 11 — The first Bombe building

People associated with Bletchley Park

External links


  • F. H. Hinsley and Alan Stripp, eds. Codebreakers: The Inside Story of Bletchley Park, Oxford University Press, Park

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